The present invention relates to improving processes of automated assembly
Several decades ago, standard manufacturing procedures used purely manual assembly for the production of nearly all multicomponent articles. These old techniques necessarily involved total human supervision over every step of the manufacturing process. By today's standards, these techniques were slow and inefficient, however they were not without merit. Intensive human attention was beneficial in that there was a very low occurrence of obvious defects, such as putting a component in the wrong place. For example it was unlikely that the head of a toy clown would be positioned at the end of the clowns foot rather than atop its neck.
Over time, technological advances facilitated increasing portions of manufacture through the use of machines and robots. Generally, these systems operate by using one or more mechanical assemblers that retrieve components from a place of storage and affix them into their proper place in the product. For instance, in placing wheels on a toy car, a mechanical assembler might retrieve a wheel from a bin of wheels and affix it to the right front axle. A second wheel would then be retrieved and affixed to the left front axle, and so on until all four wheels were in place. After affixing the wheels, the assembler might retrieve other components from other bins and affix them in place.
These automated manufacturing techniques allowed for dramatic increases in speed and efficiency, but unfortunately also created some problems. One major problem occurred because the machinery could not determine whether or not it was doing its job correctly. Therefore, if a machine was making a mistake, it would incorrectly assemble hundreds or thousands of products before an operator might notice the mistake and correct the problem. The cost of repairing or replacing duplicated mistakes is clearly excessive. Furthermore, repaired products usually suffer from decreased quality and reliability.
Some modern technologies have reduced the problem of mistake duplication. For example, automated manufacturing processes can include intermittent tests or checks. The check or test can be done by a human operator or by the machine itself. In either case, after a mistake is detected, mass duplication is prevented by quickly correcting the process or interrupting production. Unfortunately, intermittent testing increases costs and slows productivity, so it is not universally used. Even if intermittent testing were always used, it would not perfect the automated assembly process because at least one mistake must be made before it can be detected. The costs of mistakes are generally more significant than they might appear. First, a mistake incurs the cost of its own rework or replacement. Second, there is an efficiency cost caused by the down time required after a mistake is detected. Therefore, it is prudent to attempt to prevent assembly mistakes rather than correct those which have already occurred.
Many mistakes occurring in modern automated manufacturing are caused by human error in the set up of the assembly process. Specifically, assembly operators are prone to load components in the wrong places because modern articles of manufacture have increasingly large numbers of components which are often visually similar. To prevent these set up errors, well trained operators are usually very careful and deliberate in their work. However, no degree of care can totally prevent mistakes. Furthermore, careful and deliberate behavior results in very slow set up which reduces productivity.
The aforementioned problem is particularly acute in the assembly of electronic products, where components are especially numerous and physically similar. In this field, the components are small and vary only slightly, if at all, in appearance and physical dimension, and yet can have disparate electrical properties. Misplacement of electrical components usually results in the failure of the final assembly. These components are often identified only by alphanumeric combinations stamped on their surface, when surface area permits. However, surface mountable components often do not have sufficient printable area, and are identified only by markings on tubes or reels which carry the components. To compound matters, modern electronic assemblies are assembled by machines called pick and place assemblers. These assemblers are designed to retrieve components directly from industry standard reels or tubes. Therefore, the operator's primary visual contact is with the package and not the component.
Electronic products typically require several dozen different components. In a pick and place system, each tube or reel of components must be loaded in a specific place. Given the similarity of visual appearance of the reels and tubes, it is extremely easy for an operator to load a pick and place location with the wrong component. This type of error can occur during setup or replenishing of depleted components.